Fusion plate with directional holes and implant system employing the same

ABSTRACT

A fusion plate for use in fusing two bones together can include directional fastener bores that restrict the angle at which the fasteners can be positioned when inserted through the fastener bores. The fusion plate can be used in conjunction with a spacer, which may include a cavity into which the fusion plate can rest. The fusion plate can be coupled to the spacer using a coupling mechanism.

BACKGROUND

The human spine contains a series of bony segments separated by discsand coupled together with muscle, ligaments, and other connectivetissues. A large number of ailments may afflict one or more of thesecomponents. One exemplary ailment generally occurs with age as thespinal discs begin to break down, or degenerate resulting in the loss offluid in the discs, and consequently, the discs become less flexible.Likewise, the discs become thinner allowing the vertebrae to move closertogether. Degeneration also may result in tears or cracks in the outerlayer, or annulus, of the disc. Degeneration of the annulus may allowthe disc to begin to bulge outwardly. In more severe cases, the innermaterial of the disc, or nucleus, may extrude out of the disc. Inaddition to degenerative changes in the disc, the spine may undergochanges due to trauma from automobile accidents, falls, lifting, andother activities. Furthermore, in a process known as spinal stenosis,the spinal canal narrows due to excessive bone growth, thickening oftissue in the canal (such as ligament), or both. In all of theseconditions, the spaces through which the spinal cord and the spinalnerve roots pass may become narrowed leading to pressure on the nervetissue which can cause pain, numbness, weakness, or even paralysis invarious parts of the body. Finally, the facet joints between adjacentvertebrae may degenerate and cause localized and/or radiating pain. Allof the above conditions, as well as others not specifically mentioned,are collectively referred to herein as spine disease.

Conventionally, surgeons treat spine disease by attempting to restorethe normal spacing between adjacent vertebrae. This may be sufficient torelieve pressure from affected nerve tissue. However, it is oftennecessary to surgically remove disc material, bone, or other tissuesthat impinge on the nerve tissue and/or to debride the facet joints.Most often, the restoration of vertebral spacing is accomplished byinserting a rigid spacer made of bone, metal, or plastic into the discspace between the adjacent vertebrae and allowing the vertebrae to growtogether, or fuse, into a single piece of bone. The vertebrae aretypically stabilized during this fusion process with the use of fusionplates and/or pedicle screws fastened to the adjacent vertebrae. Thefusion plates used with the spacers are typically coupled to the spacerwith a first fastening means and are positioned on the spacer such thatone or more flanges extend beyond the spacer. These flanges can includeone or more holes through which pedicle screws are inserted to fastenthe fusion plate to the bone.

Although techniques for placing intervertebral spacers, plates, andpedicle screw fixation systems have become less invasive in recentyears, they still require the placement of hardware deep within thesurgical site adjacent to the spine. Extreme care needs to be taken whenplacing the hardware deep within the surgical site due to, for example,the close proximity of vessels and nerves to the surgical site. Ofspecific concern is the screws or other fastening devices used to fastenthe fusion plate to the bone. If the screws are not properly alignedwhen driven into the bone, they may impact the nerves or vessels, whichcan cause severe injury to the patient. Issues with improper orincomplete placement of the hardware at the disc space can also arise ifa screw is driven into the bone in a direction that results in the screwimpacting a screw that has already been placed in the bone.

Thus, it would be desirable to provide a fusion plate for use with animplantable intervertebral spacer that restricted the screw trajectoryvariability so as to reduce or eliminate the possibility for human errorwhen installing the fusion system.

SUMMARY

In some embodiments, a fusion plate including directional fastener boresis disclosed. The direction fastener bores restrict the angle at which afastener can be oriented when inserted in the fastener bore. This canhelp to prevent human error where a fastener is angled in a directionthat results in the fastener contacting and/or damaging areas around thebone, such as vessels and nerves. In some embodiments, the fusion plateincludes a main body portion and one or more extension side portionsextending from the sides of the main body portion. The main body portioncan include a forward face and a rearward face opposite the forwardface. The extension side portions can include a forward face, a rearwardface opposed to the forward face and one or more fastener bores. Thefastener bores generally extend from the forward face to the rearwardface of the extension side portion. The fastener bore can furtherinclude a first opening in the rearward face and a second opening in theforward face. Located intermediate the first opening and the secondopening is a throat portion. The first opening has a first diameterextending from a first side of the first opening closest to the mainbody to an opposing side of the first opening. The second opening has asecond diameter extending from a first side of the second openingclosest to the main body to an opposing side of the second opening. Thethroat portion includes a third diameter extending from a first side ofthe throat portion closest to the main body to an opposing side of thethroat portion. In some embodiments, the third diameter is shorter thanthe first and second diameters. This configuration generally forms afastener bore having an hour glass shape. Each of the first opening,second opening, and throat portion can include a perpendicular diameterthat is perpendicular to the first diameter, second diameter, and thirddiameter, respectively. The length of diameters perpendicular to thesecond and third diameters can be generally equal. The aboveconfiguration provides for a fastener to be angled in a directionparallel with the longitudinal axis of the fusion plate, but restrictsangling the fastener in a direction perpendicular to the longitudinalaxis of the fusion plate.

In some embodiments, an implant configured to be interposed betweenopposing faces of two bones to be fused together is disclosed. Theimplant can include a spacer, a fusion plate, and a plurality offasteners. The spacer can include a forward portion, a rearward portion,a top portion, a bottom portion, and two side portions, with therearward portion including at least one cavity. The fusion plate can beas described above, and can be configured to fit within the cavity inthe rearward portion of the spacer and couple together with the spacer.The fasteners can extend through the fastener bores and extend out ofthe second opening so that the fasteners can couple the implant to anendplate of the a bone segment. As described above, the angles at whichthe fasteners extending through the fastener bores can be positioned isrestricted due to the configuration of the fastener bores.

This summary provides only a general outline of some aspects of thetechnology disclosed herein. The above and other aspects of thetechnology of the present application will be apparent afterconsideration of the Detailed Description and Figures herein. It is tobe understood, however, that the scope of the application shall bedetermined by the claims as issued and not by whether given subjectmatter addresses any or all issues noted in the Background or includesany features or aspects highlighted in the Summary.

BRIEF DESCRIPTION OF THE DRAWINGS

Various examples of the present invention will be discussed withreference to the appended drawings. These drawings depict onlyillustrative examples of the invention and are not to be consideredlimiting of its scope.

FIG. 1 is a side view of three adjacent vertebra having an implantconsistent with the technology of the present application;

FIG. 2 is perspective view of a spacer consistent with the technology ofthe present application;

FIG. 3 is a top plan view of the spacer of FIG. 2;

FIG. 4 is a side view of the spacer of FIG. 2;

FIG. 5 is rearward portion elevation view of the spacer of FIG. 2;

FIG. 6 is a top plan view of a fusion plate consistent with thetechnology of the present application;

FIG. 7 is a perspective view of a fusion plate consistent with thetechnology of the present application;

FIG. 8 is a cross sectional view of a fusion plate consistent with thetechnology of the present application;

FIG. 9A is a perspective view of a fastener bore in a fusion plateconsistent with the technology of the present application;

FIG. 9B is a cross sectional view of a fastener bore from a viewperpendicular to the view shown in FIG. 8;

FIG. 10 is perspective view of a fastener consistent with the technologyof the present application;

FIG. 11 is perspective view of a connector pin consistent with thetechnology of the present application;

FIG. 12 is a cross sectional view of a fusion plate and fastenerinstrument consistent with the technology of the present application;

FIG. 13 is a cross sectional view of a fusion plate and fastenerinstrument consistent with the technology of the present application;

FIG. 14 is a cross sectional view of a fusion plate and fastenerinstrument consistent with the technology of the present application;

FIG. 15 is a perspective view of the forward face of a fusion plateconsistent with the technology of the present application;

FIG. 16 is perspective view of a cover plate consistent with thetechnology of the present application; and

FIG. 17 is a perspective view of an implant consistent with thetechnology of the present application.

DETAILED DESCRIPTION

The technology of the present patent application will now be explainedwith reference to various Figures and the like. While the technology ofthe present application is described with respect to anterior lumbarinterbody fusion (ALIF) implants, one of ordinary skill in the art wouldrecognize on reading the disclosure that the technology is applicable toother implants used in spinal fusion. For example, the technology asdescribed herein may be used for lateral interbody fusion implants,transforaminal lumbar interbody fusion (TLIF) implants, anteriorcervical discectomy (ACD) implants, and posterior lumbar interbodyfusion (PLIF) implants. Similarly, one of ordinary skill in the artwould recognize on reading the disclosure that the technology is notlimited to spinal fusion and can be applicable to other skeletalfusions, such as long bones or the like. Moreover, the technology of thepresent patent application will be described with reference to certainexemplary embodiments herein. The word “exemplary” is used herein tomean “serving as an example, instance, or illustration.” Any embodimentdescribed herein as “exemplary” is not necessarily to be construed aspreferred or advantageous over other embodiments or examples absent aspecific indication that such an embodiment or example is preferred oradvantageous over other embodiments. Moreover, in certain instances,only a single “exemplary” embodiment is provided. A single example isnot necessarily to be construed as the only embodiment. The detaileddescription includes specific details for the purpose of providing athorough understanding of the technology of the present patentapplication. However, on reading the disclosure, it will be apparent tothose skilled in the art that the technology of the present patentapplication may be practiced with or without these specific details. Insome descriptions herein, generally understood structures and devicesmay be shown in diagrams to aid in understanding the technology of thepresent patent application without obscuring the technology herein.

Referring first to FIG. 1, three vertebrae 40, 42, and 44 are provided.Each of the vertebrae 40, 42, and 44 have an anterior side 46, aposterior side 48 and lateral sides 50 (only one shown). The threevertebrae 40, 42, and 44 each have a spinous process 60.

In a normal spine, discs would reside between each of the endplates 55of vertebrae 40 and 42, and vertebrae 42 and 44. The endplates 55 formopposed bony surfaces for spinal application, but use of the technologyto be described herein is applicable to any bony segments to be fusedacross opposed facing bony surfaces. For convenience of illustration,the discs are not included in the Figures. However, injury, age, orother trauma may cause the discs to degenerate for one reason oranother. To restore proper height to a disc, for example, a surgeonwould remove all or a portion of the disc and replace it with a spacer.For example, as shown in FIG. 1, a spacer 52 may be surgically implantedin the space between vertebrae 40 and 42. As shown, spacer 52 isimplanted from the anterior side of the patient. A fusion plate 54, aswill be explained further below, is coupled to the spacer 52 and extendsover only one of the vertebrae 40 and 42 in the exemplary embodiment ofthe technology shown in FIG. 1. While shown in a spinal application, thetechnology of the present application is usable to facilitate the fusionof other bones.

Referring now to FIGS. 2 and 3, an exemplary spacer 52 is shown. Thespacer 52 is generally shaped to fit within the intervertebral space andhas a forward portion 102, which may be referred to as a posteriorportion 102, a rearward portion 104, which may be referred to as ananterior portion 104, a top portion 106, which may be referred to as asuperior portion 106, a bottom portion 108, which may be referred to asan inferior portion 108, and side portions 110. Notice that theorientation of the front (posterior), rear (anterior), left, right, top(superior), and bottom (inferior), or the like are provided forreference and should not be construed to limit the technology of thepresent application. The spacer 52 is provided to fit entirely in theintervertebral space, although in certain embodiments, the rearwardportion 104 may extend beyond the anterior ends of the vertebrae.

The rearward portion 104 of the spacer 52 can comprise a cavity 120having a depth D₁ to receive a fusion plate as will be explained furtherbelow. The spacer 52, as shown, has a void 122 providing the spacer 52with a vaguely “D” shape. Other shapes and types of spacers 52 arepossible, such as, for example, other fusion cages, dowels, and thelike. The void 122 may be packed with material to facilitate bone growthand fusion of the vertebrae 40, 42. The void 122 is generally greaterthan 20% of the surface area of the spacer 52. Alternatively to thelarge void 122, a large number of smaller bone growth channels arepossible.

A number of protrusions 116 may be provided on the top portion 106, thebottom portion 108, or a combination thereof. As best seen in FIG. 4 theprotrusions 116 form a generally shark-tooth shape that angles from theforward portion 102 towards the rearward portion 104. The protrusions116 generally resist movement of the spacer 52 out of the intervertebralspace between vertebrae 40, 42.

Still with reference to FIG. 4, the protrusions 116 are formed by afirst surface 130 forming an obtuse angle with a surface of the spacer52. The first surface 130 extends to an engaging surface 132 of theprotrusion 116. The engaging surface 132 is adapted to engage theendplates of the vertebrae 40, 42. The engaging surface 132 may beformed to a line contact, a point contact, or to a flat or convexsurface formed generally parallel to the body surface. In particular,the engaging surface 132 may be formed and shaped to conform to theanatomical shape of the associated endplates. A surface formed byconnecting the engaging surface 132 on the top and bottom portion 106,108, may be shaped to conform to the anatomical shape of the associatedendplates as well. A second surface 134 extends from the engagingsurface 132 back to the surface of the spacer 52. The second surface 134also forms an obtuse angle, but may form a right angle or be slightlyundercut. The protrusions 116 are generally of a unified constructionwith the body. The protrusions 116 generally extend over the entiresuperior and inferior surface of the implant.

Referring now to FIG. 5, an elevation view of the rearward portion 104of spacer 52 is provided. Cavity 120 has a length L₁ and a height H₁,and is sized to cooperatively engage a fusion plate, which will beexplained further below. A threaded spacer bore 138 is in the cavity120. The threaded spacer bore 138 is used, as will be explained furtherbelow, to couple the spacer 52 and the fusion plate. The threaded spacerbore 138 may have an undercut. The threaded spacer bore 138 can have afirst thread.

As can be appreciated on reading the above, the spacer 52 is providedwith a length L₁ and a height H₁ to provide an implant having areasonably low profile to fit within the intervertebral space with thespacing desired by the surgeon. To anchor the spacer 52 to the superiorand inferior vertebrae, a fusion plate 54 (FIG. 1) is provided incertain aspects of the technology of the present application. Ideally,the plate provided has as low a profile as possible.

Referring now to FIGS. 6 and 7, a fusion plate 200 consistent with thetechnology of the present application is provided. The fusion plate 200has a forward face 202 and a rearward face 204 opposite the forward face202. A sidewall 206 extends between the forward face 202 and therearward face 204. The edges of sidewall 206 may be beveled or chamferedto reduce trauma. The fusion plate 200 has a length L₂, a height H₂, anda depth D₂ to allow fusion plate 200 to cooperatively fit in cavity 120.

The fusion plate 200 can include a main body 200-a and one or moreextension side portions 200-b. The main body potion 200-a can include aplate bore 214 (described in greater detail below) which can be used tocouple the fusion plate 200 to the spacer 52. The one or more extensionside portions 200-b extend off of and away from the main body portion200-a. In some embodiments, the fusion plate includes two extension sideportions 200-b which extend away from opposite sides of the main body200-a. When the fusion plate 200 is coupled with the spacer 52, theextension side portions 200-b can be adapted to extend above or belowthe height H₁ of the spacer 52. In some embodiments, the extension sideportions 200-b are aligned so that the rearward face 204 of the mainbody portion 200-a and the extension side portions 200-b lie ingenerally the same plane. In other embodiments, the extension sideportions 200-b can extend away from the main body 200-a at an angle.

With reference now to FIGS. 6, 7 and 15, the extension side portion200-b includes one or more fastener bores 208. The fastener bores 208extend from the rearward face 204 through to the forward face 202 andprovide an opening 208-a in the rearward face 204 and an opening 208-bin the forward face 202. The fastener bores 208 are adapted to receive afastener which can extend through the fastener bore 208 and secure thefusion plate 200 to a bone, such as a vertebral body.

Each extension side portion 200-b can include one or more fastener bores208. Where more than one extension side portion 200-b is present, eachextension side portion 200-b can include the same number of fastenerbores 208. Each extension side portion 200-b could also include adifferent number of fastener bores 208. In some embodiments where morethan one extension side portion 200-b is present and each extension sideportion includes the same number of fastener bores 208, the extensionside portions 200-b and fastener bores 208 can be set up as a mirrorimage of one another. In other embodiments, the fastener bores 208 onopposing extension side portions 200-b can be arrangednon-symmetrically. As shown in FIGS. 6, 7, and 15, one embodimentincludes two extension side portions 200-b extending from opposing sidesof the main body 200-a and which include the same number of fastenerbores 208 (in this case, two each) aligned in a generally symmetricalfashion.

In some embodiments, the fastener bores 208 are adapted to restrict thedirection in which a fastener inserted in the fastener bore 208 canpivot or be angled. Generally speaking, the diameter of the fastenerbore 208 is slightly larger than the diameter of the fastener. Thisallows a fastener inserted into the fastener bore 208 to pivot 360degrees around the fastener bore 208 and be positioned at various anglesother than parallel to the axis of the fastener bore. This directionalfreedom can be desirable to a user, as it allows a surgeon to select aspecific angle at which the fastener can be driven in to a bone.However, there are also drawbacks to this amount of directional freedom.One specific example where directional freedom can be a drawback is thatit permits human error, such as allowing a user to drive a fastener in adirection that results in the fastener coming in to contact with anddamaging nerves or vessels adjacent the bone rather than the boneitself.

Accordingly, in some embodiments, the fastener bores 208 are dimensionedto restrict the directions in which a fastener can be angled onceinserted into the fastener bore 208. The direction in which the fasteneris restricted from moving is generally not limited and can be selectedbased on the specific use/surgical procedure.

With reference to FIGS. 8, 9A and 9B, a fastener bore 208 capable ofrestricting movement of a fastener inserted therethrough can generallyinclude a first opening 208-a, a second opening 208-b, and a throat area208-c located intermediate the first opening 208-a and the secondopening 208-b. The first opening 208-a includes a first diameter 270extending from a side of the first opening 208-a closest to the mainbody 200-a to an opposing side of the first opening 208-a. The secondopening 208-b includes a second diameter 280 extending from a side ofthe second opening 208-b closest to the main body 200-a to an opposingside of the second opening 208-b. The throat portion 208-c includes athird diameter 290 extending from a side of the throat portion closestto the main body 200-a to an opposing side of the throat portion 208-c.In some embodiments, the length of the third diameter 290 is shorterthan the length of the first diameter 270 and the second diameter 280such that the bore 208 has a generally hourglass shape.

The third diameter 290 will generally have a length that is onlyslightly larger than the diameter of the fastener inserted into the bore208. The first diameter 270 and the second diameter 280 are larger thanthe diameter of the fastener so that the head of the fastener can moveabout the area above the throat portion 208-c and the distal end of thefastener opposite the head can move about the area below the throatportion 208-c, with the throat portion 208-c serving as a fulcrum.

With reference to FIG. 9A and 9B, the first opening 208-a includes afourth diameter 271 that is perpendicular to the first diameter 270. Thesecond opening 208-b includes a fifth diameter 281 that is perpendicularto the second diameter 280. The throat portion 208-c includes a sixthdiameter 291 that is perpendicular to the third diameter 290. In someembodiments, the length of the fifth diameter 281 is approximately equalto the sixth diameter 291. The length of the fifth diameter 281 and thesixth diameter 291 is approximately equal to the diameter of thefastener body. The length of the fourth diameter 271 is longer than thefifth diameter 281 and the sixth diameter 291 and is approximately equalto the diameter of the fastener head.

Based upon the above described configuration for the first diameter 270,second diameter 280, third diameter 290, fourth diameter 271, fifthdiameter 281, and sixth diameter 291, a fastener inserted through thebore 208 is capable of being pivoted in a direction parallel to thelongitudinal axis AX1 shown in FIG. 6 (by virtue of the space providedabove and below the throat portion 208-c in that direction) but isrestricted from being pivoted in a direction perpendicular to thelongitudinal axis AX1 (by virtue of the absence of space above and belowthe throat portion 208-c in that direction). Accordingly, the user isfree to pick a variety of angles for the fastener in a directionparallel to the longitudinal axis AX1 but is prevented from positioningthe fastener at an angle that is perpendicular to the longitudinal axisAX1. This provides the user with some directional freedom, but not in adirection that could result in damage to, for example, nerves andvessels located adjacent the vertebral body.

In some embodiments, first opening 208-a is offset from the secondopening 208-b. With reference to FIG. 8, the first diameter 270 of thefirst opening 208-a can include a first end 270-a that is proximate themain body 200-a and a second end 270-b opposite the first end 270-a,while the second diameter 280 of the second opening 208-b has a firstend 280-a that is proximate the main body 208-a and a second end 280-bthat is opposite the first end 280-a. In some embodiments, the first end270-a of the first diameter 270 is closer to the main body 200-a thanthe first end 280-a of the second diameter 280. In some embodiments, thesecond end 270-b of the first diameter 270 is closer to the main body200-a than the second end 280-b of the second diameter 280. Thisconfiguration results in a first opening 208- a and a second opening208- b that are not aligned on top of one each other. Instead, the firstopening 208-a is offset from the second opening 208-b.

With continuing reference to FIG. 8, in some embodiments, fastener bore208 includes a first side wall portion 300 proximate the main body 200-aand a second side wall portion 301 opposite the first side wall portion300. The first side wall portion 300 can include an angled section 300-aand a vertical section 300-b. The angled section 300-a extends from thefirst opening 208-a to a point 300-c intermediate the first opening208-a and the second opening 208-b. The vertical section 300-b extendsfrom the intermediate point 300-c to the second opening 208-b. Thevertical section 300-b is vertical relative to the rearward and forwardface of the fusion plate 200, while the angled section 300-a forms anangle ALPHA with the vertical section 300-b. The second side wallportion 301 can include a vertical section 301-a and an angled section301- b. The vertical section 301-a extends from the first opening 208-ato a point 301-c intermediate the first opening 208-a and the secondopening 208-b. The angled section 301-b extends from the intermediatepoint 301-c to the second opening 208-b. The vertical section 301-a isvertical relative to the rearward and forward face of the fusion plate200, while the angled section 301-b forms an angle BETA with thevertical section 300-a. In some embodiments, the intermediate point300-c is closer to the forward face of the fusion plate 200 than theintermediate point 301-c.

In some embodiments, the angle ALPHA is equal to the angle BETA and theangled section 300-a is parallel to the angled section 301-b. In someembodiments, the angle of the angled section 300-a and 301-b sets amaximum angle at which the fastener can be angled when inserted in thefastener bore 208.

The above described configuration for the fastener bore 208 can berotated any number of degrees in order to change the direction in whichmovement of the fastener is restricted. For example, rotating the abovedescribed fastener bore 90 degrees would limit the movement of thefastener so that it can be pivoted in a direction perpendicular to thelongitudinal axis AX1 of the fusion plate, but not in a directionparallel to the longitudinal axis AX1 of the fusion plate.

As mentioned above and referring now to FIGS. 6, 7, and 15 the main body200-a of the fusion plate 200 can further comprise a plate bore 214. Theplate bore 214 is adapted to be aligned with threaded spacer bore 138.In one aspect of the technology, the fusion plate 200 is coupled to thespacer 52 using a threaded connector that extends through the plate bore214 and the spacer bore 138 and engages with threading located on theinner walls of each.

With reference to FIG. 10, the spacer 52 and the fusion plate 200 arecoupled to the superior and inferior vertebrae in this exemplary aspectby a plurality of fasteners 236. The fasteners 236 may be anyconventional fasteners, such as, for example, a bone screw 236. The bonescrew 236 may comprise a head 238 and a shaft 240 having threads T. Thefasteners 236 are adapted to be threaded into the endplates of thevertebrae 40, 42 by extending the fasteners through the fastener bores208. The fastener bores 208 described herein are configured to allow thefasteners to be positioned at various angles to provide greaterflexibility with respect to the best direction in which the fastenerscan be inserted into the bone to ensure a secure coupling between theimplant and the bone.

The fasteners 236, as is conventionally known, have a tendency toreverse thread or back-out of the vertebrae 40, 42, and the fusion plate54. A lock may be provided to inhibit the fasteners 236 from reversethreading. In certain aspects of the technology, the lock may be a coverplate. Referring now to FIG. 16, a cover plate 260 is provided that isusable with the fusion plate 200. The cover plate 260 has a first face262 and a second face 264 opposite the first face 262. The cover plate260 may be shaped to fit into a recess 266 in the fusion plate 200, asshown in FIGS. 6 and 7. The cover plate 260, as shown, generally has amain body portion 268 with a cover plate bore 270.

A connecting pin, which will be explained further below, couples thecover plate 260 to the fusion plate 200. The cover plate bore 270 alignswith the plate bore 214 described above. A plurality of arms 278 extendfrom the main body portion 268. The arms 278 extend from the main bodyportion a sufficient distance such that at least a distal end 282 of thearm extends over fastener bore 208. The distal end 282 of the arm, thus,resists the ability of the fastener 236 to reverse thread from theimplant.

As can be appreciated, the shape and size of the cover plate 260 dependsin part on the shape and size of fusion plate 200. The shape and size ofthe cover plate 260 specifically shown in FIG. 16 is designed for usewith the fusion plate 200 shown in FIGS. 6 and 7. Generally, each arm oncover plate 260 is associated with a single fastener bore 208.

As described above, the cover plate bore 270 generally aligns with theplate bore 214. The cover plate 260 is coupled to the fusion plate 200using a connecting pin 286 as shown in FIG. 11. The connecting pin 286has a head 288 and a shaft 290. The shaft 290 has a proximal portion 294proximate to the head 288, a distal portion 296 distal from the head288, separated by a medial portion 298. The proximal portion 294 has afirst thread T₅ that is designed to cooperatively engage the threads ofthe cover plate 260. The medial portion 298 is shown as being threadlessand provides a transition from the proximal portion to the distalportion. The distal portion 296 has a second thread T₆ that is designedto cooperatively engage the threads of an inner threaded bore in thefastener used to couple the fusion plate 200 to the spacer 52. Theconnecting pin 286 has length L₄ and couples the cover plate 260 to thefusion plate 200.

Referring now to FIG. 17, an implant 300 consistent with the above isprovided. The implant 300 includes spacer 52. The protrusions 116 areshown on the top (or superior) portion. The cavity 120 in the rearwardportion 104 has the fusion plate 200 therein. The fastener bores 208 ofthe fusion plate 200 are located on the extension side portions 200-b ofthe fusion plate. The fasteners 236 extend through the fastener bores208 and can be positioned at a variety of angles permitted by theconfiguration of the fastener bores 208. The cover plate 260 is providedwith arms 278 covering the fastener bores 208. The connecting pin 286 isthen moved into cover plate bore 270.

In some embodiments, the fusion plate described above can be usedwithout a spacer. In such embodiments, the fusion plate is secured to,for example, vertebral bodies using fasteners, but the fusion plate isnot coupled to a spacer. In some embodiments, no spacer will be lodgedbetween vertebral bodies when the fusion plate is secured to thevertebral bodies. In some embodiments, a cover plate can be used withthe fusion plate even when the fusion plate is not used with a spacer.

The technology of the present application also includes methods forimplanting the apparatus described above. While the methodology isprovided in certain discrete steps, one of ordinary skill in the artwill recognize that the steps identified may be broken into multiplesteps or multiple steps may be combined into a single step. Moreover,the sequence of events provided may be altered or rearranged withoutdeparting from the technology of the present application.

With that in mind, the surgeon would first determine the appropriatespacer to be used. In spinal applications, the spacer may be sized torestore the height corresponding to the height of a health vertebra. Inother applications, the spacer may be sized to most readily promotefusion or the like.

Once the appropriate spacer is identified, the surgeon may implant thespacer in the fusion cite. This step may be carried out using anyimplanting steps known to those of ordinary skill in the art, includingthe use of specialized tools or instruments to implant the spacer at thefusion site. In an exemplary implantation step, the forward face of thespacer is implanted into the fusion site and the spacer is moved intothe fusion site until a desired length of the spacer is implanted in thefusion site. The rearward face may jut out of the fusion site, may beflush with the bone segments, or may be inside the fusion site.

In some embodiments, the spacer is implanted with a coupling mechanismalready coupled to the spacer. For example, a threaded connector may bethreaded into the spacer bore prior to implanting the spacer in thefusion site. The coupling mechanism can then be used to couple a fusionplate to an implanted spacer. Alternatively, the coupling mechanism canbe added to the spacer after the spacer has been implanted.

Next, a fusion plate would be selected and coupled to the spacer alreadyimplanted in fusion site. The fusion plate can be coupled to the spacerusing any mechanisms known to those of ordinary skill in the art. Asnoted above, a threaded connector may be used to allow the fusion plateto be snap fit to the spacer. For example, the protrusions on theslotted head may be compressed and fitted into the fusion bore until asnap fit is formed between the slotted head and the fusion plate. Inother embodiments, the fusion plate is coupled to the implanted spacer,followed by using a fastener to secure the fusion plate to the spacer. Afastener can be inserted through the fusion plate bore and spacer bore,which can each include threads selected to mate with threads on thefastener.

The surgeon would next use fasteners to couple the implant to the boneysegments, such as the superior and inferior vertebrae for a spinalapplication. The surgeon has the option of positioning the fasteners ata variety of angles permitted by the fastener bores. Likewise, thesurgeon is prohibited from positioning the fasteners at various anglesnot permitted by the fastener bore and which ideally prevent the surgeonfrom causing the fasteners to contact an area other than the bone.

In some embodiments, an instrument adapted for use with the fusion platedescribed herein can be used in order to position and drive thefasteners into the boney segments. With reference to FIG. 12, theinstrument 500 can generally include a shaft portion 510 and a fastenerengagement end 520 positioned at a distal end of the shaft portion 510.In some embodiments, the fastener engagement end 520 comprises aspherical shape that is shaped and configured to mate with the fastenerbore 208 and allow the instrument 500 to sweep through the range ofangles permitted by the fastener bore 208. The rounded shape of thefastener engagement end 520 allows the slide back and forth along thevertical portion 301-a and the angled portion 300-a of the fastener bore208. In some embodiments, diameter 521 of the fastener engagement end520 is larger than a distance 522 between intermediate point 300-c andintermediate point 3001-c so that the fastener engagement end 520 cannotpass completely through the fastener bore 208. Instead, the fastenerengagement end 520 rests against the angled portion 300-a and thevertical portion 301-a and pivots about this area to position thefastener at a desired angle. As also shown in FIG. 12, the fastenerengagement end 520 may include a distal vertical end 523 where thespherical shape straightens out at the very distal end of the instrument500.

Another instrument suitable for use with the fusion plate describedherein is shown in FIGS. 13 and 14. The instrument 600 includes a shaftportion 610 and an fastener engagement end 620. Rather than having aspherical shape, the fastener engagement end 620 of instrument 620 has ageometry that mates perfectly with the fastener bore 208. As shown inFIG. 13, this includes a vertical wall 621 for mating with the verticalportion 301-a and an angled wall 622 for mating with the angled portion300-a. The instrument 600 may also include a distal vertical end 623where the angled wall 622 straightens out to form a vertical segment atthe very distal end of the instrument 600.

With reference to FIG. 14, a feature of the instrument 600 is thatrotating the instrument 600 180 degrees and positioning it in thefastener bore 208 aligns the instrument 600 at the most extreme anglepermitted by the fastener bore 208. As shown in FIG. 14, when positionedin this rotated configuration, the angled wall 622 rests against thevertical portion 301-a and the straight wall 621 rests against theangled portion 300-a.

Finally, a cover plate that corresponds to the fusion plate is selectedand coupled to the fusion plate. For example, the connecting pin may bethreaded through the cover plate bore and fusion plate bore into theinternal threads of the threaded connector to couple the cover plate,fusion plate, and spacer.

The implant may be supplemented with bone growth promoting substances tofacilitate fusion of adjacent vertebrae between spinous processes,laminae, transverse processes, facets, and/or other spinal structures.The bone growth promoting substances may be spaced from the implant,placed adjacent the implant, sandwiched between the implant andunderlying bone, placed inside the implant, coated onto the implant,and/or otherwise placed relative to the implant. If it is coated ontothe implant, it may cover the entire implant or only selected portionsof the implant such as the extensions, fasteners, spinous processcontacting portions of the spacer, and/or other portions.

In some embodiments, bone growth promoting materials are placed withinthe spacer before or after the spacer is implanted but before the fusionplate is coupled to the spacer. When bone grown promoting materials areplaced within the spacer after it has been implanted but before thefusion plate has been coupled to the spacer, the surgeon has improvedaccess to place the materials in the spacer as well as improvedvisibility.

As used herein, bone growth promoting substances may include bone paste,bone chips, bone strips, structural bone grafts, platelet derived growthfactors, bone marrow aspirate, stem cells, bone growth proteins, bonegrowth peptides, bone attachment proteins, bone attachment peptides,hydroxylapatite, calcium phosphate, other suitable bone growth promotingsubstances, and/or combinations thereof.

The implant and any associated cerclage or other components may be madeof any suitable biocompatible material including among others metals,resorbable ceramics, non-resorbable ceramics, resorbable polymers, andnon-resorbable polymers. Some specific examples include stainless steel,titanium and its alloys including nickel-titanium alloys, tantalum,hydroxylapatite, calcium phosphate, bone, zirconia, alumina, carbon,bioglass, polyesters, polylactic acid, polyglycolic acid, polyolefins,polyamides, polyimides, polyacrylates, polyketones, fluoropolymers,and/or other suitable biocompatible materials and combinations thereof.

Various methods, systems and devices for treating spinal fractures aredisclosed. While detailed descriptions of one or more embodiments havebeen provided above, various alternatives, modifications, andequivalents are possible. Therefore, the above description should not betaken as limiting the scope of possible embodiments, which is defined bythe appended claims.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thescope of the invention. Accordingly, the invention is not limited exceptas by the appended claims.

We claim:
 1. An intervertebral implant comprising: a spacer configuredto fit between the opposing endplates of two vertebrae to promote fusionof the two vertebrae, the spacer comprising a proximal end including arecess defined at least in part by two opposing members that each extendin a proximal direction, each of the two opposing members comprising asidewall including a convex curvature in a plane formed by the proximalend; a fusion plate coupleable to the proximal end comprising: a bodyportion comprising a forward face, a rearward face opposed to theforward face, and opposing concave lateral sidewalls extending from theforward face to the rearward face of the body portion, the opposingconcave lateral sidewalls connecting a first extension and a secondextension of the body portion; the first extension including a firstbore extending from the rearward face to the forward face; and a firstfastener extendable through the first bore to couple the implant to anendplate of a first vertebra; wherein the body portion of the fusionplate is directly receivable between the two opposing members of therecess and the convex sidewalls of the two opposing members matinglyengage the concave lateral sidewalls of the body portion of the fusionplate.
 2. An implant configured to be interposed between opposing facesof two bones to be fused together, the implant comprising: a spacerconfigured to fit between the opposing sides of the two bones to promotefusion of the two bones, the spacer comprising a forward portion, arearward portion, a top, a bottom, and two side portions, the rearwardportion comprising at least one cavity defined in part by two opposingmembers that each extend in a rearward direction, each of the twoopposing members comprising a convex cavity sidewall, wherein the convexcavity sidewall includes a convex curvature in a plane formed by therearward portion; a fusion plate coupleable to the spacer comprising: amain body portion comprising a forward face, a rearward face opposed tothe forward face, and opposing concave lateral sidewalls extending fromthe forward face to the rearward face of the main body portion; a firstextension side portion comprising a forward face and a rearward faceopposed to the forward face and extending away from a first side of themain body, wherein the first extension side portion is configured toextend beyond at least one of the top or the bottom of the spacer; and afirst bore in the first extension side portion extending from therearward face to the forward face, the bore comprising a first openingin the rearward face comprising a first diameter extending from a firstside of the first opening closest to the main body to an opposing sideof the first opening; a second opening in the forward face comprising asecond diameter extending from a first side of the second openingclosest to the main body to an opposing side of the first opening; and athroat portion located intermediate the first opening and the secondopening and comprising a third diameter extending from a first side ofthe throat portion closest to the main body to an opposing side of thethroat portion; wherein the third diameter is shorter than the firstdiameter and the second diameter; and a plurality of fastenerscomprising at least a first fastener extendable through the first boreto exit out of the second opening and configured to couple the implantto an endplate of a first bone; wherein the main body portion of thefusion plate is directly receivable between the two opposing members ofthe at least one cavity and the convex cavity sidewalls of the twoopposing members matingly engage the concave lateral sidewalls of themain body portion of the fusion plate.
 3. The implant of claim 2,wherein the first diameter of the first opening has a first endproximate the main body and a second end opposite the first end and thesecond diameter of the second opening has a first end proximate the mainbody and a second end opposite the first end, and wherein the first endof the first diameter of the first opening is positioned closer to themain body than the first end of the second diameter and wherein thesecond end of the first diameter is positioned closer to the main bodythan the second end of the second diameter.
 4. The implant of claim 2,wherein: the first bore includes a first side wall portion proximate themain body and a second side wall portion opposite the first side wallportion; the first side wall portion includes an angled portionextending from the first opening to a first point intermediate the firstopening and the second opening and a vertical wall portion extendingfrom the first point to the second opening; and the second side wallportion includes a vertical portion extending from the first opening toa second point intermediate the first opening and the second opening andan angled portion extending from the second point to the second opening.5. The implant of claim 2, wherein the spacer further comprises a spacerbore extending from the forward portion to the rearward portion andwherein the main body portion of the fusion plate further comprises afusion plate bore extending from the forward face to the rearward faceand the fusion plate is coupled to the spacer with a fastener thatextends through the fusion plate bore and the spacer bore.
 6. Theimplant of claim 5, wherein the fusion plate bore and the spacer boreare coaxially aligned when the fusion plate is disposed in the cavity.7. The implant of claim 2, wherein the first bore limits movement of theat least one fastener extending therethrough in a directionperpendicular to a longitudinal axis of the fusion plate.
 8. The implantof claim 2, further comprising a recess formed in the rearward face ofthe main body and the first extension side portion and adapted forreceiving a cover plate.
 9. The implant of claim 4, wherein the firstside wall angled portion is oriented parallel with the second side wallangled portion.
 10. The implant of claim 4, wherein the second point iscloser to the rearward face than the first point.
 11. The implant ofclaim 2, wherein the first extension side portion includes a second boreidentical to the first bore.
 12. The implant of claim 11, wherein thesecond bore is located lateral to the second bore.
 13. The implant ofclaim 2, wherein the fusion plate further comprises a second extensionside portion extending away from a second side of the main body portionthat is opposite the first side of the main body portion.
 14. Theimplant of claim 13, wherein the second extension side portion comprisesa first bore identical to the first bore in the first extension sideportion.